Ultra small clusters of gold nanoshells detected by SNOM

Abstract

Metal nanoshells are a type of nanoparticle composed by a dielectric core and a metallic coating. These nanoparticles have stimulated interest due to their remarkable optical properties. In common with metal colloids, they show distinctive absorption peaks at specific wavelengths due to surface plasmon resonance. However, unlike bare metal colloids, the wavelengths at which resonance occurs can be tuned by changing the core radius and coating thickness. One basic application of such property is in medicine, where it is hoped that nanoshells with absorption peaks in the near−infrared can be attached to cancerous cells. In this paper, we study the changes of optical response in visible and near infrared wavelengths from single to randomly distributed clusters of nanoshells. The results were obtained using a novel formulation of Mie theory in evanescent wave conditions, with a finite−difference time−domain (FDTD) simulation and experimentally on BaTiO

Detection of Intracellular Gold Nanoparticles: An Overview

“…The resolution is 10 nm or better. An application of the SNOM to detect intracellular AuNSs (BaTiO3 core ~100 nm +Au shell ~40 nm) has been developed by D’Acunto et al [ 38 , 39 , 40 , 41 ]. In this study, the SNOM were used in air in collection mode with an oblique angle ( θ = 45°) illuminating laser light of 780 nm, Figure 4 .…”

“…High-resolution dynamic contrast-enhanced photoacoustic imaging in vivo has been recently demonstrated using acoustic nanomodulators [ 37 ]. In turn, Scanning Near-Optical Microscopy (SNOM) has been employed to detect and localize 120–150 nm AuNPs (nanoshells) absorbing light in the near-infrared range exploiting the biological transparency window [ 38 , 39 , 40 , 41 ]. By default, in the rest of the text we will indicate the NPs of spherical geometry with the term AuNP, and we will specify the other NP geometries (AuNS or AuNR) when necessary.…”